#include <iostream>
using namespace std;
#include <iomanip>
using std::setw;
#include <cmath>
#include <cstdlib>

double  distance(double a1[],double a2[]);

int main()
{
	double a1[2]={0,0}, a2[2]={3,4};
	double dis=distance(a1,a2);
	cout << dis;
}

double distance(double a1[],double a2[])
{
	double dis=0;
	dis=(a1[0]-a2[0])*(a1[0]-a2[0])+(a1[1]-a2[1])*(a1[1]-a2[1]);
	dis=sqrt(dis);
	return dis;
}
